I grew up in the Boston area and currently live in Seattle, so I know both of them from experience.
Cost of living
Seattle hands down. Sure, it’s expensive here in Seattle, but Boston takes it to a whole new level.
Transportation
Both have decent bus systems, but at least it’s possible to drive in Seattle if you are so inclined. It is also more bike-friendly if you swing that way. However, you are more likely to need a car in Seattle than in Boston; we are pretty spread out.
I have yet to be stuck in traffic more than an hour on my 25-mile commute. In Boston, it would often take me that long to go less than half that distance. Overall, advantage Seattle.
Weather
Both get cold and snowy. Seattle will get into the 20s-30s and the occasional snowstorm. Boston will go sub-zero and fucking bury you, and your little dog Toto too.
But Boston handles 18 inches of snow in a night better than Seattle handles 3 inches. People know how to drive in the snow, they have snowplows, and they salt the roads. (Granted, that will eat your car from the bottom up, but hey!) Seattle drivers get stupid, put chains only on the front of RWD vehicles, and generally shut everything down at the first snowflake.
Arts and culture
Seattle spawned Nirvana. My favorite local band, Abney Park is dong pretty well too; they just put out a novel and a twelfth album. Boston doesn’t have the Slut Walk. Last I knew, they didn’t have Hempfest or Bumbershoot (an annual 74-acre art/music festival). Boston does have it’s own things though, so that is really subjective.
One thing that still trips me out though; people here look at a building put up in 1910 and consider it old whereas I am used to living placed built closer to the Civil War, and Boston has many places a couple of centuries older than that. Education is better in Boston though. Harvard, MIT… well, we’ll just end there because Seattle has nothing on that level. UW is cool and all, but not on that plane.
Ease of entry into a new social group
The East coast is generally less friendly, and that is putting it mildly. I have lived in all four corners of the continental US, and visited nine countries on three other continents, and I have to say that New England has the rudest, most stand-offish people of anywhere I’ve been. Not to say that we are all bad, but if you are one of those cheery people who believes that strangers are merely friends you haven’t met yet, prepare to get dirty looks, fingers, and requests to perform odd sex acts.
People almost anywhere in the world other than the Northeast are more friendly and open. More importantly, they are more laid-back.
It’s late, so I will end there for now.
@johnpowell I visited Seattle years before I moved here. Trust me, the Seattle you see as a tourist isn’t the Seattle you see as a Seattlite.